Japan's ambassador to the United States expressed concern Thursday about legislation pending in Virginia that would require school books to use "East Sea" as well as "Sea of Japan" to name the waters between Japan and the Korean Peninsula.

"I wonder if it is fair in primary and secondary education to (only) back one side over a matter of international dispute," Kenichiro Sasae told a group of Japanese reporters in Washington.

Tokyo maintains that the Sea of Japan is the only internationally established name for the waters, while Seoul maintains that the East Sea name was historically more prevalent before Japan annexed the Korean Peninsula in 1910 and suppressed its political influence.

"I'm concerned about this kind of move," Sasae said. "We will make efforts to make sure the move (in Virginia) does not spill over" to other parts of the United States.

Virginia is home to an increasing number of Korean-Americans, mainly in northern areas close to Washington. Some counties in adjacent Maryland have already decided to use textbooks that list both the Japanese and South Korean names for the waters, despite objections from Tokyo.